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PostPosted: 17 Mar 2012 03:58 
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indranilroy wrote:
I don't see much fault in Shivji's calculations (Assuming uniform acceleration). He is just using the basic mechanical equations and back of the envelop calculations which are not way off.

But we have an easier way to calculate this. Please notice the 1000 ft distance markers. The nose-wheel is up at (roughly) 2000 ft marker and the plane takes off. The think the MLG becomes airborne is 200 more feet.

So that translates to 610 mtrs for nose-wheel up and 670 mtrs for MLG up.


Indranil, where do you see the 1000ft distance markers? I am no math guru (in fact quite handicapped in math by the standards on BR) so can't really comment on Shivji's numbers. However, what I did do was simply looked at the closest runway marker (denoted by white stripes) that the LCA takes off at, and then verified that length via google maps - what i found was that the LCA took off just before the 6th marker on the strip (starting from a standstill at HAL runway, direction didn't matter), and that was how I came to the conservative 750 meter distance.

But YES, I redid the same thing again, and I would agree that wheel-up happened around 600 meters just BEFORE the 5th marker lines.

I know it is not the most sophisticated or even accurate method, but is my best guesstimate :)

CM.


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PostPosted: 17 Mar 2012 04:08 
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CM sahab,

the 1000 feet markers are the black rectangular things sticking out by the side of the runway. they are visual cues used to mark how many 1000 feet to go to the end of the runway.


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PostPosted: 17 Mar 2012 04:18 
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Yeah, I thought of using those as markers as well but didn't know what distance exactly they were marking, even worse, they seemed non equidistant on google maps, so just went with runway stripes.


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PostPosted: 17 Mar 2012 06:14 
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Vashishtha wrote:
Aircraft during takeoff roll DON'T have constant acceleration..


No. For acceleration to change forces must change.

The brakes are released when the afterburner is lit. After that is done the thrust cannot increase any more. The after burner is not turned off until the aircraft is in the air - so no change in thrust.

Other variables are weight (no significant change in 20 seconds)

Headwind/tailwind I am ignoring.

acceleration = force/mass

if force and mass are constant the acceleration is constant.


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PostPosted: 17 Mar 2012 08:01 
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Force subsumes mass. Change in direction changes acceleration.


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PostPosted: 17 Mar 2012 08:05 
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shiv wrote:
Vashishtha wrote:
Aircraft during takeoff roll DON'T have constant acceleration..


No. For acceleration to change forces must change.

The brakes are released when the afterburner is lit. After that is done the thrust cannot increase any more. The after burner is not turned off until the aircraft is in the air - so no change in thrust.

Other variables are weight (no significant change in 20 seconds)

Headwind/tailwind I am ignoring.

acceleration = force/mass


A small correction to the quoted statement is needed as static thrust is not equal to dynamic thrust.
if force and mass are constant the acceleration is constant.[/quote]


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PostPosted: 17 Mar 2012 08:55 
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As speed increases drag should also increase. So if engine thrust is held constant, increase in drag will cause a decrease in acceleration.

Which is why people using visual markers are reporting longer takeoff distances.


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PostPosted: 17 Mar 2012 09:23 
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Gurneesh wrote:
As speed increases drag should also increase. So if engine thrust is held constant, increase in drag will cause a decrease in acceleration.

Which is why people using visual markers are reporting longer takeoff distances.


I am sure you are right. But the data we have is that nose lift off is at 240 kmph. Nosewheel lift occurs in 15 seconds
You have the time taken. You have velocity and the point of time the nosewheel lifts. Calculating distance from that is trivial.


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PostPosted: 17 Mar 2012 09:33 
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shiv wrote:
Gurneesh wrote:
As speed increases drag should also increase. So if engine thrust is held constant, increase in drag will cause a decrease in acceleration.

Which is why people using visual markers are reporting longer takeoff distances.


I am sure you are right. But the data we have is that nose lift off is at 240 kmph. Nosewheel lift occurs in 15 seconds
You have the time taken. You have velocity and the point of time the nosewheel lifts. Calculating distance from that is trivial.


Shivji, I agree with your back of the envelop calculations ... I would do the same simplifications (of uniform acceleration) for a quick estimate.

But I would not say the bold part in your response. The displacement is the area under the velocity time graph. In straight-line motion, this is the area under the speed-time curve. So, technically distance cannot be inferred by just knowing the time and the final speed :-) . for example the distance will be in increasing order with the came final speed and time taken if the speed curve is concave (double differentiation of speed > 0), than when speed curve is a straight line joining 0 to final speed (acceleration is constant), than when speed curve is convex (double differentiation of speed < 0).


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PostPosted: 17 Mar 2012 10:32 
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Just an illustration of the above

Image

If we take the area under the curve (which is the distance traveled), it will be different for the three cases even when the final velocity and the time taken is same for all three (and not to mention that the plane is always accelerating in all three cases).


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PostPosted: 17 Mar 2012 10:37 
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I think that apart from 40 Mark-1 LCA we should order another 20 Mark-1 for additional squadron and 20 twin seater Mark-1 to be used as AJT/CAS etc, which should give LCA Mark-1 a respectable run while giving time to Mark-2 to get going.

Further apart from AMCA we should plan for LCA Mark-3 (semi stealth like MAKO) with Kaveri-Snecma engine to cater for any delay in AMCA


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PostPosted: 17 Mar 2012 10:47 
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Just concentrate the MK-1 as a point defence fighter. The IAF has enough strike aircraft for the moment. The LCA can be turned into a true multirole if needed when the MK.II program matures. As it is, being a light fighter and a limited if not decent range it makes more sense as an A-2-A aircraft. It is imperative that the LCA suceeds if the IAF is going to reach its goal of 60 sqd with over 1000 fighters by 2030.


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PostPosted: 17 Mar 2012 11:30 
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Is there a possibility to modify LCA MkI into a MkII a/c later on?

The engine is heavier AFAIK but will this cost be prohibitive to do the modification?


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PostPosted: 17 Mar 2012 11:49 
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Mk2 is supposed to be longer fuselage (longer nose for aesa radar back end and a longer area behind cockpit for addl fuel and to fix wave drag or something...). this means a bigger wing also.

so no way Mk1 can change to Mk2...


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PostPosted: 17 Mar 2012 11:50 
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koti wrote:
Is there a possibility to modify LCA MkI into a MkII a/c later on?

The engine is heavier AFAIK but will this cost be prohibitive to do the modification?


kotiji Not sure but last i heard, they were planning to increase the length by a meter and some wing dimension reduction.
So i guess they would not modify considering all the trouble ($$$ considerations), engine weight, inlet design change, new wing dimensions, extra length.

oops just saw singhaji has already answered it.


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PostPosted: 17 Mar 2012 11:56 
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>>so no way Mk1 can change to Mk2

What about engine upgrade alone?

Chirag ji, The cost of upgrade can be offset(to some extent) by ordering more MkI now and later modifying them with the newer engine.
If the IAF may be ok with 40 f404, it may be ok with 80 f414'ed MkI too. I think we will be getting more birds rolling a lot quicker this way then waiting for MkII to order big at a later point.


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PostPosted: 17 Mar 2012 12:12 
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that would totally waste the life of the 404IN20 engine.


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PostPosted: 17 Mar 2012 12:17 
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koti wrote:
>>so no way Mk1 can change to Mk2

What about engine upgrade alone?

Chirag ji, The cost of upgrade can be offset(to some extent) by ordering more MkI now and later modifying them with the newer engine.
If the IAF may be ok with 40 f404, it may be ok with 80 f414'ed MkI too. I think we will be getting more birds rolling a lot quicker this way then waiting for MkII to order big at a later point.


Yes only engine is possible. but in this case(414) inlet has to change for extra thrust. but I Agree numbers can offset the cost
and i wish they get MK1 in numbers than waiting for another FOC (for MK-II)which will only be done after xxx number of hours of testing.

PS please take out the ji from me :D

Singhaji has a point!


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PostPosted: 17 Mar 2012 12:52 
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Singha wrote:
that would totally waste the life of the 404IN20 engine.

Ya.
Any exchange with OEM for more F414 or sell off to JAS/F-18 operators possible?
I read that around 4000 F404's are operational workdwide in Hornets alone.


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PostPosted: 17 Mar 2012 13:34 
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no need to change Mk1 to Mk2 by a MLU. when IAF has enough Mk2's the Mk1's can be used for the roles OCU is used for.


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PostPosted: 17 Mar 2012 15:17 
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the hornets (F-18C/D) use a older model of 404 engine. the superhornets use 414. the older hornet operators like canada/swiss/australia/spain will likely just retire them in the next decade.


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PostPosted: 17 Mar 2012 18:09 
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Have a production line with M1 going one with some 20 per year and when M2 arives have good no with that. Now that we have a decent M1 which is more than sufficient for most of the S**t of pakiland and old rubbsih from Panda we can have a good no of them also. Further these M1s can be used extensively for petrolling, training etc to get their life span hours compleated as early as possible so that they can be retired early to be replaced by M2s sat in a decade or so. Wasting the model which is suitable and avaliable for production is stupid and in fact criminal when we have such a low no of aircrafts at present.


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PostPosted: 17 Mar 2012 19:38 
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The conversion of Mk 1 to Mk 2 will be illogical. They will have to change the airframe, engine and the avionics. Then what is left? However, Mk 1 can have its own MLU, not necessarily as per Mk 2 standards, but, can have commonality. Sending it to ASTE is also not an option 'afterwards,' it has to be now.

As someone pointed out that it should be retained as pure a2a; for CAP and other peace time duties like OCU.


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PostPosted: 17 Mar 2012 19:53 
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Gurneesh and Indranilroy thanks. I have some doubts posted in the Off topic thread linked belo
viewtopic.php?f=24&t=5689&p=1256698#p1256698


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PostPosted: 17 Mar 2012 20:54 
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Rahul M Post subject: Re: LCA News and DiscussionsPosted: 17 Mar 2012 13:34


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Location: racetrack pattern over BRFATA. no need to change Mk1 to Mk2 by a MLU. when IAF has enough Mk2's the Mk1's can be used for the roles OCU is used for.




Mr.Rahul I am with Bharat rakshak from long time.When I responde to somebody writing then I have a problem.How to lighter in box I have seen here all the time.Then below I wuold write my comments.I hope you do under stand what I am trying to say.Please explain me.if you did't understand what I am saying and PLEASE delete this.My E-mail is kchr@comcast.net


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PostPosted: 17 Mar 2012 21:05 
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I think you need to press the quote button in top right of that individual post.


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PostPosted: 17 Mar 2012 21:06 
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Singha wrote:
I think you need to press the quote button in top right of that individual post.


like this?


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PostPosted: 17 Mar 2012 21:14 
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Thank you.


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PostPosted: 17 Mar 2012 23:37 
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I haven't seen the eject handle in LCA. Where is it located?
Or is it that all the Martin-Baker seats have the same configuration?


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PostPosted: 18 Mar 2012 02:37 
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I thought we are using our own (arde) ejection seat. Are we still using MB ejection seats for LSPs?
vic wrote:
Further apart from AMCA we should plan for LCA Mark-3 (semi stealth like MAKO) with Kaveri-Snecma engine to cater for any delay in AMCA

+1. Actually the LCA-Mk3, should be a twin engine one - the same would suffice [ge/kaveri-snecma] to begin. Need the divertless inlets, perhaps variable internally with pak-fa like controls [also used for stealth deflections].

Need to concentrate on the tail signatures as well, as both pak-fa and raptor have left a big question on thermal signatures. there are some h20 based solution to chemical driven to reduce thermal radiations. one could also think about a regular exhausts with a missile warning sensor that immediately sprays water or has a retractable trailing pod to deceive the missile seeker at least 25-50ft behind.

retractable technology needed for refueling.

internal weapons bay and its designs, we need multiple prototypes here for various designs we can think off.

the ever needing AESA especially with local al/GaN modules, and specially train from the baseline spec of El/m 2052 variant.

moving away from delta config!

blended body, reduced rivets or advanced skin engineering, etc.

there is a ton of work on stealth that is needed. we need LCA Mk3 for that.

If GoI/MoD is not already budgeting for this, then ADA/DRDO is making a mistake. In addition, I want the word snecma removed from genuine kaveri, at any cost.


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PostPosted: 18 Mar 2012 09:10 
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Cain Marko wrote:
Yeah, I thought of using those as markers as well but didn't know what distance exactly they were marking, even worse, they seemed non equidistant on google maps, so just went with runway stripes.


Thats becoz in some areas they are placed in alternate fashion on either side of the runway.

LCA take off happened between 2000 ft - 3000 ft. And I think ~750 meter figure might be accurate.


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PostPosted: 18 Mar 2012 11:11 
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http://maps.google.com/maps/place?ftid= ... CCA&dtab=2
Which markings CM, are you talking about?


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PostPosted: 18 Mar 2012 11:36 
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Ok admittedly a very late question to the party but why does the LCA fuselage ride so high ? In other words why is the height from the main fuselage to the ground so high? Is it for weapons attachments clearance and mid line external drop tanks attachment only or something else? Once the wheels are retracted the plane is obviously a gorgeous looking bird but does look a shade ungainly on the ground in clean config.. Not that this matters at all but obviously some weight saving can be achieved by appropriately sizing the height of the undercarriage.. It could also be the height required to ensure the LCA does not do a tail scrape on landing but there could be other reasons as well that escape me..


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PostPosted: 18 Mar 2012 13:01 
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koti wrote:
Is there a possibility to modify LCA MkI into a MkII a/c later on?

The engine is heavier AFAIK but will this cost be prohibitive to do the modification?


F414 engine requires higher airflow, is heavier and bigger; hence, the LCA Mk2 version with changes to accommodate it. Plus, fuselage has been lengthened slightly.

IMO, instead of changing the F404 engine on LCA Mk1, if ADA could try to reduce its weight by 500kgs (or so) then the thrust with F404 will match with the original design parameters. Or for MLU, go with Kaveri JV (~90KN) which will be ready and inducted in time for Mk1 MLU in 2030.


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PostPosted: 18 Mar 2012 14:50 
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Jayram wrote:
Ok admittedly a very late question to the party but why does the LCA fuselage ride so high ? In other words why is the height from the main fuselage to the ground so high? Is it for weapons attachments clearance and mid line external drop tanks attachment only or something else? Once the wheels are retracted the plane is obviously a gorgeous looking bird but does look a shade ungainly on the ground in clean config.. Not that this matters at all but obviously some weight saving can be achieved by appropriately sizing the height of the undercarriage.. It could also be the height required to ensure the LCA does not do a tail scrape on landing but there could be other reasons as well that escape me..


uc height normally a function of attitude (angle) at take off and more so landing to give adequate clearance of tail


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PostPosted: 18 Mar 2012 16:15 
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SaiK wrote:
+1. Actually the LCA-Mk3, should be a twin engine one - the same would suffice [ge/kaveri-snecma] to begin. Need the divertless inlets, perhaps variable internally with pak-fa like controls [also used for stealth deflections].

Need to concentrate on the tail signatures as well, as both pak-fa and raptor have left a big question on thermal signatures. there are some h20 based solution to chemical driven to reduce thermal radiations. one could also think about a regular exhausts with a missile warning sensor that immediately sprays water or has a retractable trailing pod to deceive the missile seeker at least 25-50ft behind.

retractable technology needed for refueling.

internal weapons bay and its designs, we need multiple prototypes here for various designs we can think off.

the ever needing AESA especially with local al/GaN modules, and specially train from the baseline spec of El/m 2052 variant.

moving away from delta config!


blended body, reduced rivets or advanced skin engineering, etc.

there is a ton of work on stealth that is needed. we need LCA Mk3 for that.

If GoI/MoD is not already budgeting for this, then ADA/DRDO is making a mistake. In addition, I want the word snecma removed from genuine kaveri, at any cost.


All the blue points call for increased weight. There is no reason why the resultant bird should be in the LCA catagory, It better fits the MCA specs and that is what MCA is intended to be IMO.
Quote:
moving away from delta config!

Why?


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PostPosted: 18 Mar 2012 21:31 
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AMCA is planned to have tail plus a larger clipped/shaped [may be more diamond-ish] wing delta.


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PostPosted: 21 Mar 2012 05:43 
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Q.: Is the test pilot Gp Capt KK Venugopal the same person who did the 1st Saras test flight as Sqdn Leader?


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PostPosted: 21 Mar 2012 06:05 
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Jayram wrote:
Ok admittedly a very late question to the party but why does the LCA fuselage ride so high ? In other words why is the height from the main fuselage to the ground so high? Is it for weapons attachments clearance and mid line external drop tanks attachment only or something else? Once the wheels are retracted the plane is obviously a gorgeous looking bird but does look a shade ungainly on the ground in clean config.. Not that this matters at all but obviously some weight saving can be achieved by appropriately sizing the height of the undercarriage.. It could also be the height required to ensure the LCA does not do a tail scrape on landing but there could be other reasons as well that escape me..


I have never thought of it that way. I have not felt that the fuselage is high, but that the LCA fuselage is a cylinder that is flattened flattened from side to side, so that the side to side diameter is more than the up-down (dorso-ventral) diameter if you exclude the intakes. That makes the upper part of the fuselage appear high.

Just my impression


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PostPosted: 21 Mar 2012 13:05 
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Flight test update

LCA-Tejas has completed 1807 Test Flights successfully. (20-Mar-2012).
(TD1-233,TD2-305,PV1-242,PV2-218,PV3-335,LSP1-70,LSP2-202,PV5-36,LSP3-47,LSP4-46,LSP5-72,LSP7-1)

From

LCA-Tejas has completed 1801 Test Flights successfully. (15-Mar-2012).
(TD1-233,TD2-305,PV1-242,PV2-217,PV3-334,LSP1-70,LSP2-201,PV5-36,LSP3-46,LSP4-46,LSP5-70,LSP7-1)


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